Triphenyltin pesticides in sea water as immunotoxins for tunicates

Triphenyltin derivatives (TPTs, Fentin) cause a severe immunotoxicity in tunicates, having significant inhibitory effects on yeast phagocytosis by hemocytes of the colonial ascidian Botryllus schlossen — TPTC > TPTA > TPTH — in a concentration-dependent manner. The same order of inhibition is observed for Ca2+-ATPase activity, suggesting that the inhibition of this enzyme and of phagocytosis may be closely linked. Addition of 20 μg/ml calmodulin is able to reverse the inhibition of Ca2+-ATPase activity by TPTs, but not to restore the phagocytosis index. These results support the hypothesis that mitochondrial oxidative phosphorylation may also be involved, as O2− production is inhibited —TPTA > TPTC > TPTH — in a concentration-dependent manner, but not restored by calmodulin. Besides, TPTs cause some morphological changes without cytolysis, suggesting an interaction with cytoskeletal components, whereas viability is not affected up to 100 μM for TPTA and TPTC, and 1 mM for TPTH.